Interpretive Summary: Mile-a-minute is an exotic annual barbed vine that is now invasive in the northeastern USA, Mississippi, and Oregon and is a target of biological control efforts. In 2010, diseased mile-a-minute plants were found along the Firtina River, near Ardesen, Turkey. Disease symptoms were irregular dark-colored necrotic lesions along leaf margins and smaller irregular reddish-colored lesions on leaf blades. Diseased leaves were sent to the BSL-3 containment facility at the Foreign Disease-Weed Science Research Unit of USDA/ARS in Frederick Maryland. A fungus identified as Colletotrichum gloeosporioides was isolated from these leaves, and the disease was reproduced with the fungus on mile-a-minute plants from Maryland. Specimens of the fungus were deposited in the U.S. national fungus collection. Further tests are planned to determine the suitability of the fungus for biological control of mile-a-minute in the U.S.

Technical Abstract:
Mile-a-minute (Persicaria perfoliata (L.) H. Gross; family Polygonaceae) is an exotic annual barbed vine that is now invasive in the northeastern USA, Mississippi, and Oregon and is a target of biological control efforts. In July, 2010, diseased P. perfoliata plants were found along the Firtina River, near Ardesen, Turkey. About 40 plants (vines) in the area were diseased. All plants were about 1 m long × 0.3 m wide. Disease symptoms were irregular dark-colored necrotic lesions along leaf margins and smaller irregular reddish-colored lesions on the lamellae of leaves. Symptomatic leaves were sent to the USDA/ARS Foreign Disease-Weed Science Research Unit laboratory. Portions of the leaves with lesions were excised and surface disinfested in 10 percent aqueous bleach solution. Disinfested leaf pieces were incubated at 20-25 degrees C in sterile moist chambers. Numerous waxy sub-epidermal acervuli with 84-µm-long (mean) black setae were observed in all of the lesions after 2-3 days of incubation. Conidiophores within the acervuli were simple, short, and erect. Conidia were one-celled, hyaline, ovoid to oblong, falcate to straight, 12.3 to 18.9 × 3.0 to 4.6 um (mean 14.3 × 3.7 um). Pure cultures were obtained by transferring conidia masses onto 20 percent V-8 juice agar. Appressoria, formed 24 h after placing conidia on dialysis membrane over V-8 juice agar, measured 6.4 to 10.0 × 5.1 to 7.2 um (mean 7.5 × 6.6 um). These characters conformed to the description of Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz. A voucher specimen was deposited with the U.S. National Fungus Collections (BPI 882461). Nucleotide sequences for the internal transcribed spacers (ITS 1 and 2) were deposited in GenBank (JN887693) and, after BLAST analysis, aligned 100 percent to more than 75 previously identified isolates of C. gloeosporioides (teleomorph=Glomerella cingulata) in GenBank. Conidia from 14-day-old cultures were spray-inoculated, in a suspension of 1.0 × 106 conidia ml-1 water plus 2 percent sucrose and 0.5 percent gelatin, onto healthy stems and leaves of five 30-day-old P. perfoliata plants. Another 4 plants were spray-inoculated five weeks later with an aqueous conidial suspension of 1.2 × 106 conidia ml-1. Lesions developed on leaves and stems of all inoculated plants after 7 days, and symptoms were the same as observed in the field. Each plant was rated weekly for disease severity based on a 0-10 rating scale where “0” = no disease symptoms and “10”= 100 percent symptomatic tissue. After 67 days, the average disease rating of the plants from the first inoculation was 4.8 + 1.9. After 30 days, the average disease rating of the plants from the second inoculation was 4.3 + 3.2. C. gloeosporioides was re-isolated from all inoculated plants, and the morphology of the re-isolated pathogen was the same as that of the initially isolated pathogen. To our knowledge, this is the first report of anthracnose caused by C. gloeosporioides on P. perfoliata.